Hot plate, and hob having a hot plate

ABSTRACT

A hot plate has a hot-plate body from metal, having an upper side and a lower side. At least one heating element is disposed on the lower side of the hot-plate body. The upper side of the hot-plate body is configured so as to be flat, for setting up a cooking vessel to be heated. The upper side of the hot-plate body in an external region has an encircling planar region which lies in a plane, or which forms a plane, respectively, wherein the upper side, radially within the planar region, has at least one internal region which is concavely depressed, which in relation to the planar region is depressed by between 0.05 mm and 1 mm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Application No. EP 16155081.9, filed Feb. 10, 2016, the contents of which are hereby incorporated herein in its entirety by reference.

TECHNOLOGICAL FIELD

The invention relates to a hot plate, and to a hob having a hot plate.

BACKGROUND

Hot plates for the use in hobs or stoves for cooking, respectively, have been known for a long time, for example from EP 957661 B1 or U.S. Pat. No. 5,010,235. Hot plates of this type have a hot-plate body from a metal casting or steel, on the upper side of which a cooking vessel to be heated is set up. Heating helices in an insulation material are disposed as heating elements in depressions that are separated by webs on a lower side of the hot-plate body. Such a hot plate is usually inserted from above into a hot-plate opening in a hob plate of a hob, and by way of a projecting periphery bears thereon. From below, the hot plate is covered by a cover disk or the like, and is fastened or braced, respectively, to the hob plate by way of a counterbearing that covers the hot-plate opening.

Hobs having hot plates of this type are indeed still manufactured nowadays, since the latter are cost-effective and very robust in terms of application. However, a very slow or sluggish heating behavior, respectively, and a sub-optimal energy efficiency of the hot plates are seen as disadvantageous.

BRIEF SUMMARY

The invention is based on the object of providing a hot plate as mentioned at the outset, and a hob as mentioned at the outset, by way of which problems in the prior art may be solved, and by way of which it is in particular possible for the manufacturing and installation of a hot plate to be simplified, or for the operational behavior and the efficiency of the hot plate in the installed state to be improved, respectively.

This object is achieved by a hot plate, and by hobs. Advantageous and preferred design embodiments of the invention are the subject matter of the further claims, and will be explained in more detail hereunder. Herein, many of the features are mentioned only in the context of the hot plate or only in the context of the hob. Irrespectively, the features are intended to apply independently to both the hot plate as well as to a hob. The wording of the claims by way of explicit reference is incorporated into the content of the description.

It is provided that the hot plate has a hot-plate body having an upper side and a lower side. The hot-plate body per se is composed of metal, in particular of steel or iron, or cast iron, respectively. The hot-plate body is advantageously monolithic, or a single integral metal part, respectively, that is thus in particular cast and subsequently machined, in particular on the upper side. At least one heating element, advantageously configured as a heating helix that is embedded in an insulation material and press-fitted into the lower side, is disposed on the lower side of the hot-plate body. The upper side of the hot-plate body in turn is configured so as to be flat, so as to be able to set up a cooking vessel to be heated thereon. Flat in this context is not to be understood to be inevitably precisely level or planar, but rather flat or advantageously without any deviations from a planar shape having elevations or depressions of more than 3 mm, advantageously of more than 0.5 mm.

According to the invention it is provided for a hot plate that the upper side of the hot-plate body has an external region and an internal region, wherein the external region surrounds the internal region. An encircling planar region which lies in a plane, or which forms a plane, respectively, is provided in the external region. The planar region is thus planar. Advantageously, the planar region is continuously encircling, without any interruption. It may be provided for the planar region that the latter is machined by way of post-machining, in particular by turning. On account thereof, the planar region may have a structure, in particular in the form of encircling or concentric or spiral-shaped rings, respectively. For the rings it should be provided however that the upper sides thereof form an afore-mentioned plane, or lie in a planar plane. The planar region thus need not inevitably be completely smooth in compact manner, but form or define a planar plane, respectively, or lie in a plane.

The upper side, radially within this afore-described planar region, furthermore has at least one internal region which is concavely depressed. The depressed internal region may directly adjoin the planar region, but not necessarily. The concavely depressed internal region advantageously has a circular shape and is rotationally symmetrical with a center of the hot-plate body, or the upper side of the latter.

A hot plate which in the external region has a planar upper side, or a planar bearing face for a cooking vessel to be set up, respectively, is thus achieved. The hot-plate upper side within this planar set-up face, or within the planar region according to the invention, respectively, has a concavely depressed internal region, that is to say is somewhat drawn downwards. On account thereof, it is to be avoided in all circumstances that a set-up cooking vessel, by virtue of production tolerances or potentially also by virtue of burned-in contaminations, bears on a region in a relatively punctiform manner, thus severely compromising the heat transfer between the hot-plate body and the cooking vessel.

It may advantageously be provided that no region of the hot-plate body, or of the upper side thereof, respectively, projects upwards beyond the planar region. A positive set-up of a cooking vessel, having a good heat transfer, may thus be ensured.

In a design embodiment of the invention it is possible for the planar region to be spaced apart from an external edge or an external periphery of the hot plate that defines a maximum radial extent of the hot plate or of the hot-plate body by a maximum of 5% of the radius of the hot-plate body. This spacing is thus intended to be a few millimeters (mm), for example 1 mm to 5 mm. In an advantageous design embodiment of the invention, only an oblique and sharply downward chamfered hot-plate periphery, or a peripheral chamfer, respectively, is provided radially outside the planar region, in particular so as to directly adjoin the latter. However, this chamfered periphery is then quite obviously no longer suitable for a heat transfer to a cooking vessel to be set up, merely forming a mechanically stable and risk-free external termination of the hot-plate body. Such a hot-plate periphery may be 1 mm to 5 mm wide. Usually, a spillage periphery or the like from stainless steel, such as is known from the prior art, may downwardly adjoin the former. However, the spillage periphery serves only as visually appealing and sealed connection to a hob plate into which the hot plate is inserted. The spillage periphery does not have any influence on the invention.

A width of the planar region may be between 1 mm and 30 mm, advantageously between 3 mm and 10 mm. In other words, such a width may be between 1% and 20%, in particular between 3% and 10% of the radius of the hot-plate body. This means that the planar region indeed forms a certain significant planar bearing face for a good heat transfer to a cooking vessel to be set-up. However, it is at the same time obvious that a significant part of the upper side of the hot plate, in particular more than 50%, is formed by the internal region that is surrounded by the planar region and that in turn by way of the concavely depressed shape according to the invention runs or lies below the latter, respectively. However, this concavely depressed shape may advantageously have only a very minor depth such that the internal region, for example by way of thermal expansion of the hot plate during operation, expands or curves slightly upwards, respectively, and thus, for a yet improved heat transfer, in certain circumstances bears on the lower side of a set-up cooking vessel.

In an advantageous design embodiment of the invention, the encircling planar region has an approximately consistent width. This facilitates production, in particular subtractive machining of the upper side that is carried out by turning. Moreover, a hot plate according to the invention may be round, in particular have a rotationally symmetrical upper side. However, this is not mandatory, rectangular or square basic shapes, respectively, of a hot plate also being possible, in particular having rectilinear external edges and rounded corners. In this instance, an externally encircling planar region also has a substantially square or rectangular shape, respectively.

The concave depression of the internal region within the planar region, when viewed in the cross section, may be variously configured. On the one hand, this may be a conical shape, that is to say having substantially rectilinear flanks in the sectional illustration. Such a conical shape, specifically by way of an aforementioned subtractive machining by turning, is relatively easy to produce since no complex programmed controller is required. Alternatively, the internal region may be a concavely depressed arc, that is to say a segment of a circle in the sectional illustration. Other intermediate shapes and parabolas or the like are also possible. The profile of this depression advantageously is strictly monotonous and steady, without jumps or steps or corners, respectively.

A maximum depth of the concave depression of the internal region below the planar region may be between 0.05 mm and 1 mm, advantageously between 0.08 mm and 0.3 mm. This demonstrates that this concave depression of the internal region lies only slightly below the encircling planar region such that any potentially existing air gap in relation to the lower side of a set-up cooking vessel is very minor, so as to provide as good a heat transfer as possible. In particular, the deepest region of the depressed internal region may have the afore-mentioned dimension below the encircling planar region if and when a single depression is provided within the planar region.

In an alternative design embodiment of the invention, an internal region within the encircling planar region may indeed have an afore-described curvature which as a depression having a continuous profile would have a maximum depth between 0.05 mm and 0.1 mm below the plane of the planar region. In the case of this alternative design embodiment of the invention, a central zone that in relation to the concave depression is yet again depressed is however provided in a central region of the internal region, in particular about a center of the hot plate. The depth of the central zone is significantly greater, or the concave curvature of the central zone is configured so as to be significantly more intense, respectively, and the central zone may have a depth of 0.3 mm to 3 mm below the plane of the planar region. Depressed central zones of this type, having a depression in the range of millimeters below a set-up face of the hot plate are known in principle from the prior art. The central zones are intended to improve the expansion behavior of the hot-plate body during heating. Furthermore, hot-plates are often not provided with heating elements in this central zone, or no heating elements are provided on the lower side in relation to the central zone, respectively, so that as minor an air gap as possible in relation to the lower side of the cooking vessel is less important here.

It applies to the afore-described yet again depressed central zone that the latter, as has been described above in the context of the internal region, may either have a conical shape, an arcuate shape, or any other shape as a cross section. Advantageously, the profile of the central zone is likewise strictly monotonous and steady, or without interruptions, jumps, or steps or corners, respectively.

A yet again depressed central zone of this type may have a radius between 5% and 30% of the radius of the hot-plate body. The radial width of the yet again depressed central zone may thus be between that of the planar region and that of the internal region outside the central zone.

It may be advantageously provided that the yet again depressed central zone extends in a radially outward manner only so far that on a lower side of the hot plate no more heating elements are provided opposite the former, or so as to have the same radius or spacing from a central axis of the hot plate. On account thereof, it is ensured that no heating output is discharged in a region in which the effectiveness would be minor due to the depressed central zone lying thereabove.

A hob according to the invention has at least one hot plate according to the invention, such as has been described above. Furthermore, the hob has a hob plate which is advantageously composed of metal or stainless steel, respectively. The hob plate has a hot-plate opening into which the hot plate is inserted, advantageously from above. Herein, the hot plate by way of a laterally projecting periphery bears beyond this hot-plate opening, or bears on the upper side of the hob plate, respectively. To this end, a usual spillage periphery as mentioned at the outset in the form of a stainless-steel ring or the like may be used, this however being irrelevant in this context. In order for the hot-plate to be fastened to the hob, a counterbearing is attached to the hot plate from below and fastened or screwed to the hot plate in a central region. A screw connection is considered to be usual and simple; however, latching bolts or clamping bolts or the like could also be used.

The counterbearing engages across the hot plate and at least three bearing points bears on the lower side of the hob plate, wherein the counterbearing also engages across the hot-plate opening. These at least three bearing points have a specific distance from one another, in particular a mutual spacing of an arc angle of at least 45°, or of at least 10% of the circumference of the hot-plate opening, respectively. In this way it is ensured that the bearing points are truly distributed and thus, by contrast to usual counterbearings from the prior art which only have two opposite bearing points, cause a distribution of the forces introduced in the hob plate and thus also acting on the hot-plate body that is not only on either side of a line which runs through the center of the hot-plate body. The bearing points are advantageously equally distributed, or are equally spaced apart from one another, respectively. Specifically, this fastening by way of a counterbearing according to the prior art may lead to buckling or sagging of the hot-plate body, which of course negatively impacts the planar upper side thereof. This is prevented by the plurality of bearing points, or by at least three or four mutually spaced-apart bearing points, respectively.

Such a counterbearing may be configured in various ways. According to a simple design embodiment, the counterbearing is configured at least in a Y-type manner, having three arms, or in a cruciform manner, having four arms that emanate from a center, or quasi mutually intersect therein, respectively. Advantageously, the arms may be mutually disposed at identical angles, or the bearing points on the lower side of the hob plate that are formed by the respective arms may also be equally spaced apart from one another, respectively. An introduction of force in this instance is particularly equally distributed or uniform, respectively. Instead of three or four arms, six or eight arms, that is to say a star-shaped counterbearing, may also be provided. To this end, this may be a special and correspondingly configured metal part; alternatively, these may be a plurality of separate arms which are placed on top of one another and are then twisted in relation to one another. Such arms may be composed of a flat sheet-metal plate, having at least one bent or upright external edge for reinforcement.

In one alternative design embodiment of the invention, the counterbearing may have the shape of a curved disc which in particular is circular, having a diameter that is larger than the diameter of the hot-plate opening in the hob plate. Such a counterbearing may likewise be connected to the hot plate in a central region, as has been described above. The counterbearing in the external region may largely bear on the lower side of the hob plate, in particular in a completely encircling manner. To this end, the counterbearing does not even have to be a particularly precisely made part, since the external periphery of the counterbearing will bear on the lower side of the hot plate in a uniform and encircling manner for bracing the hot plate on the counterbearing at the latest as fastening in the central region of the hot plate and tightening of a screw or other fastening takes place. An opening for routing through an electric connector to the hot plate should be present in such a planar counterbearing, wherein the opening advantageously runs within an encircling periphery of the counterbearing, or is spaced apart from the periphery by at least 1 cm or 2 cm, in order for there not to be any weakening of the encircling bearing on the lower side of the hob plate. Producing such a counterbearing having a curved disc shape as a deep-drawn part from a simple sheet-metal plate also does not represent any major problems. In certain circumstances, such a disc-shaped counterbearing may also replace another cover plate or cover feature on the lower side of the hot plate.

In a yet further design embodiment of the invention, such a fastening, having a special counterbearing, to a hob or to a hob plate, respectively, may also be performed for a normal known hot plate instead of a hot plate according to the invention, the normal known hot plate thus not having the design embodiment of the upper side of the hot-plate body according to the invention. Here too, bending or buckling, respectively, of the hot-plate body may be prevented by a counterbearing having offset or distributed bearing points, respectively, this significantly improving the planarity of the upper side of the hot-plate body also in the case of normal known hot plates.

Apart from the claims, these and further features are also derived from the description and the drawings, wherein the individual features may be implemented individually or in a plurality thereof in the form of a sub-combination in the case of an embodiment of the invention and in other fields, and may represent advantageous embodiments that per se are capable of being protected and which are claimed herein. The subdivision of the application into individual paragraphs and subtitles does not limit the statements made therebelow in terms of the general applicability of the latter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Further advantages and aspects of the invention are derived from the claims and from the description hereunder of various preferred exemplary embodiments of the invention that are explained hereunder by means of the schematic figures. In the drawings:

FIG. 1 shows a sectional illustration through a first design embodiment according to the invention of a hot plate having a single concavely depressed internal region within an encircling planar region.

FIG. 2 shows a further alternative design embodiment of a hot plate according to the invention, as a modification of that of FIG. 1, having an additional yet again depressed central zone.

FIG. 3 shows a hob according to the invention, having two hot plates according to the invention that are inserted into a hob plate and are held from below by counterbearings.

FIG. 4 shows a lower view of the hob of FIG. 3, having two dissimilarly configured counterbearings.

FIG. 5 shows a detailed oblique illustration of the disc-shaped counterbearing that is illustrated on the left in FIG. 4.

DETAILED DESCRIPTION

A right-hand region of a hot plate 11 according to the invention that has a hot-plate body 13 is illustrated in a section in FIG. 1. The hot-plate body 13 has a substantially flat upper side 15 which however does not inevitably have to be completely planar by any means. An encircling planar region 17 which is configured as a circular ring having a consistent width, the latter being indicated thereabove by the short lines, is provided in the external region. This width may be 10 mm. The planar region 17 is completely planar, or lies completely in one plane, or in other words does not project beyond a plane on which the planar region 17 nevertheless chiefly or largely or completely bears, respectively, or which plane the planar region 17 defines, respectively. This means that micro-depressions, a rough surface, or concentric channels that are usually created by rotating final machining of a casting of which the hot-plate body 13 is composed, having a depth of significantly less than 0.3 mm, are not considered a deviation from this planarity. The upper edges or upper sides of the channels in this instance lie substantially in the mentioned planar plane.

An internal region 19 according to the invention which lies below the planar plane of the planar region 17, or which is concavely depressed, respectively, is provided so as to be radially within the planar region 17. Herein, this depression may either be spherically concave, as has been explained at the outset, such that in a heavily enlarged lateral illustration of FIG. 1 the internal region 19 would be a segment of a circle, having the lowest point in the center. Alternatively, the internal region 19 may be concavely depressed in a conical manner, such that the flanks on the left and the right would substantially be straight lines, and would be mirror-symmetrical in relation to a central axis of the hot plate 11 that is illustrated with dashed lines. This is more readily possible by rotating machining, as has been mentioned above. In yet another further alternative design embodiment of the invention, the depressed internal region 19 may also have any other curved shape. A transition from the internal region 19 to the planar region 17 may be gradual or soft, respectively, in certain circumstances having a very slightly configured edge at the transition. The planar region 17 in the plan view has an annular-ring shape, the depressed internal region 19 having a circular shape.

The internal region 19 lies in the center in the region of the dashed-line central axis that has the greatest depth, or the deepest point, respectively, approximately 0.1 to 0.2 mm below the plane of the planar region 17. This suffices as a depression in order for the technical advantages that are achieved by the invention. A foreseeably very small air gap results towards the lower side of a set-up cooking vessel. However, the air gap is not capable of being illustrated in the drawing, even at a great enlargement, but is readily comprehensible by means of the illustration shown herein. The diameter of the hot plate herein is approximately 18 cm.

An external edge 21 of the hot-plate body 13 runs so as to be radially outside the planar region 17. A peripheral chamfer 22 is configured above this external edge 21. Thus, the planar region 17 does indeed not form the outermost region of the hot plate 11, or of the hot-plate body 13, respectively, but does at least lie very far to the outside, or there is identifiably no region that is conceived for setting up a cooking vessel to be heated radially outside thereof, respectively.

Except for the upper side 15, or the planar region 17, respectively, and for the depressed internal region 19, the hot plate 11 is configured according to the prior art. An encircling flange periphery 26 which radially lies somewhat within the external edge 21 is moulded to the outside of the lower side 15 of the hot-plate body 13. Encircling webs 28 are moulded to the lower side 25 so as to be radially within the flange periphery 26, wherein a heating helix 29 that is embedded in an insulation material runs as a heating element in the depressions that are formed on account thereof. A projecting central dome 31 having a thread 32 provided therein is configured in a centric manner about the dashed-line central axis. The central dome 31 lies somewhat below the flange periphery 26 but in certain circumstances may also protrude beyond the latter.

In the case of the further hot plate 111 according to the invention of FIG. 2, an externally encircling planar region 117 is again provided as an annular ring on an upper side 115 of a hot-plate body 113. The width of the annular ring may again be approximately 10 mm, at a diameter of the hot plate 111 of 18 cm. A depressed internal region 119 which in terms of shape and depth may be configured in a manner similar to that of the internal region 19 in the case of the hot plate 11 of FIG. 1, specifically also as an annular ring, is provided radially within the planar region 117, or in certain circumstances so as to directly adjoin the latter. The depth of the annular ring, or the lowest point thereof, in the case of a continuous profile would lie approximately 0.1 to 0.2 mm below the plane of the planar region 117. Again, this is not capable of being illustrated in the drawing; please refer to the explanations above.

A yet again depressed central zone 120 which advantageously is rotationally symmetrical or which is configured so as to be circular if and when the entire hot plate 111 is circular, is provided in a centric manner about the central axis of the hot plate 111 that is illustrated with a dashed line. The yet again depressed central zone 120 in the center may have a maximum depth of approximately 1 mm to 1.5 mm as the deepest point, this under certain circumstances being somewhat more or less. As can be seen from the sectional illustration, the yet again depressed central zone 120 does not have a very gradual transition to the radially outward and adjacent internal region 119, but drops in a relatively rapid manner to more than half the maximum depth. This means that bearing thereon by a set-up cooking vessel to be heated can definitely not be achieved herein by way of the design embodiment and the depth of the depressed central zone 120. The function of this depressed central zone 120 corresponds to that of other usual hot plates known from the prior art; in particular, the issue is the expansion behavior of the hot-plate body 113 during heating.

As can be seen, it may be provided according to a generally advantageous aspect of the invention that the yet again depressed central zone 120 in the radial direction extends only as far as heating elements (not illustrated here) would be provided on a lower side 115 between the webs 128. On account thereof, it is ensured that no heating output is discharged in the region of the central zone 120 where effectiveness would in any case be extremely minor.

A hob 35 according to the invention, having a hob plate 36 known per se, advantageously from a stainless steel sheet, is illustrated in a simplified sectional illustration in FIG. 3. Two hot-plate openings 37, advantageously of identical configuration and under certain circumstances of dissimilar diameters, into which the two hot plates 11 according to the invention are inserted, are provided in the hob plate 36. Alternatively, hot plates as known from the prior art may also be inserted. In practice, the hob plate 36 in the region of the hot-plate openings 37, as can be assumed from the lower view of FIG. 5, has a collar that is pulled upward. As is known to a person skilled in the art, this collar bears externally on the flange periphery 26, in the transition of the latter to the horizontal region of the external lower side 25 of the hot-plate body 13 towards the external edge 21. An encircling stainless-steel ring is also push-fitted over the flange periphery 26 therebetween, the stainless-steel ring in turn externally engaging across the upper end edge of the hot-plate opening 37 and bearing on the upper side of the hob plate 36. In this way, a visually appealing and potentially even tight connection protecting against contamination may be achieved. This, however, corresponds to the prior art.

A counterbearing 40 is attached from below to each hot plate 11, so as to radially engage across the latter and in particular also across the hot-plate openings 37. The counterbearing 40 then in each case bears on the lower side of the hob plate 36, outside the hot-plate opening 37. The counterbearing 40 is braced in relation to the hot plate 11 by means of a screw 43 in the aforementioned threads 32 in the central dome 31 of the hot plates 11, the counterbearing 40 pulling the hot plate 11 firmly from below against the hob plate 36. On account thereof, an unshiftable connection is achieved on the upper side of the hob 35.

It can be readily seen from the sectional illustration of FIG. 3 that in those case in which a counterbearing 40, as is the case in the prior art, is only a web or an arm, running from left to right, a specific force is exerted on the hot plate 11 or on the hot-plate body 13 that will bend the latter, in particular downward in the plane of the drawing. Even the hob plate 36 does not prevent this since ever thinner sheet-metal plates are often being used. On account thereof, a planarity of the upper side of the hot plate is compromised, in particular in the case of known hot plates as well as also in the case of a hot plate according to the invention. For this reason, the counterbearings 40 are advantageously configured according to an aspect of the invention as is illustrated in the lower view of FIG. 4, this specifically also applying to known hot plates. A first counterbearing 40 a which has the shape of a curved disc, as has been described at the outset, is illustrated on the left in FIG. 4. The diameter of the disc of the counterbearing 40 a is larger, for example 5 mm to 20 mm larger, than that of the hot-plate opening 37 that directly adjoins the flange periphery 26 (illustrated with dashed lines) of the hot plate 11, so to speak. The disc 40 a has an opening 41 a through which a connection cable 12 to an electric connector of the hot plate 11 may be routed. Details in this context will yet be described hereunder in the context of FIG. 5.

As an alternative to a planar disc-shaped counterbearing 40 a, so to speak, a counterbearing may also be configured as is known in the prior art, that is to say in the manner of a web, but having at least four arms or two crossed webs, respectively. The four arms 42 or 42′, respectively, run in a crossed manner and thus bear on all four distributed bearing points on the lower side of the hob plate 36, being firmly held by the force of the screw 43. On account thereof, not quite as uniform bearing and encircling mounting as is the case in the counterbearing 40 a on the left in FIG. 4 is achieved, however.

In the detailed illustration of FIG. 5 which does not require too much detailed explanation, a counterbearing 240 a in the form of a disc similar to that of FIGS. 3 and 4 is illustrated in detail. The afore-described elevation of the periphery of the hob plate 36 of the hob 35 towards the hot-plate opening 37 can be clearly seen herein, the counterbearing 240 a for this reason herein bearing in a depressed manner so to speak on the lower side of the hob plate 36, in a portion that adjoins the elevation in a radially inward manner. However, this is not mandatory. Centric fastening of a hot plate (not illustrated herein) which by way of the afore-described flange periphery of the hot plate lies radially within the counterbearing 240 a is provided by means of a threaded bolt 243 with a nut. Furthermore, two bolts 245 that project from the lower side of the hot plate and penetrate corresponding openings in the counterbearing 240 a are provided as anti-rotation protection. Above all, a connection installation 212 (not to be explained in more detail herein) for an electric connector of the hot plate 11 that penetrates an opening 241 a in the counterbearing 240 a can be seen.

Usually, hot plates on the lower side thereof have yet another cover feature which substantially covers the region between the flange periphery 26 and the central dome 31, from which thus an electric connector protrudes in a similar manner as illustrated in FIG. 5. Such a cover feature may also be provided in the case of the hot plates according to the invention, or in the case of the hobs according to the invention, having a fastening of the hot plates to the hob plates. Alternatively, when a disc-shaped and largely closed or covering counterbearing, respectively, according to FIG. 4 on the left and to FIG. 5, is used, such a cover feature may be dispensed with, since the hot plate in the installed state on the hob after all is at the latest covered by the disc-shaped counterbearing. 

That which is claimed:
 1. A hot plate comprising: a hot-plate body, wherein: said hot-plate body has an upper side and a lower side; said hot-plate body is composed of metal; at least one heating element is disposed on said lower side of said hot-plate body; said upper side of said hot-plate body is configured so as to be flat, for setting up a cooking vessel to be heated; said upper side of said hot-plate body comprises an external region in which an encircling planar region is provided, said encircling planar region lying in a plane or forming a plane, respectively; and said upper side, radially within said planar region, comprises at least one internal region being concavely depressed.
 2. The hot plate according to claim 1, wherein said hot-plate body is composed of cast iron.
 3. The hot plate according to claim 1, wherein said planar region is spaced apart from an external edge of said hot plate having a maximum radial extent by a maximum of 5% of a radius of said hot-plate body, wherein only an oblique and sharply downward chamfered hot-plate periphery, radially outside said planar region, encircles said planar region.
 4. The hot plate according to claim 1, wherein said encircling planar region comprises a width of 1 mm to 30 mm.
 5. The hot plate according to claim 1, wherein said encircling planar region comprises a width of 3 mm to 10 mm.
 6. The hot plate according to claim 1, wherein said encircling planar region comprises a width between 1% and 20% of a radius of said hot-plate body.
 7. The hot plate according to claim 6, wherein said encircling planar region comprises a width between 3% and 10% of a radius of said hot-plate body.
 8. The hot plate according to claim 1, wherein said encircling planar region comprises a consistent width.
 9. The hot plate according to claim 1, wherein said internal region is concavely depressed, said concavity comprising a shape or curvature, respectively, of a cone or of an arc.
 10. The hot plate according to claim 9, wherein said internal region comprises a single concave depression.
 11. The hot plate according to claim 10, wherein a maximum depth of said concave depression below said encircling planar region is 0.05 mm to 1 mm.
 12. The hot plate according to claim 9, wherein, in a central region of said internal region, a central zone that in relation to said concave depression is yet again depressed and that comprises a depth between 0.3 mm to 3 mm below said encircling planar region is provided.
 13. The hot plate according to claim 12, wherein a maximum depth of said concave depression of said internal region below said encircling planar region is 0.05 mm to 1 mm.
 14. The hot plate according to claim 13, wherein said depressed central zone is concavely curved, having a more intense curvature than a curvature of said internal region.
 15. The hot plate according to claim 12, wherein no heating elements are provided below or opposite said depressed central zone, respectively, on a lower side of said hot plate.
 16. A hob having at least one hot plate according to claim 1, wherein: said hob comprises a hob plate comprising a hot-plate opening in said hob plate into which said hot plate is inserted, said hot plate by way of a laterally projecting periphery of said upper side of said hot-plate body projecting beyond said hot-plate opening, wherein for fastening said hot plate to said hob, a counterbearing is attached to said hot plate from below and in a central region is fastened or screwed to said hot plate; and said counterbearing engages across said hot-plate opening and bears on said lower side of said hob plate at least three bearing points, said bearing points being mutually spaced apart by an arc angle of at least 45°.
 17. The hob according to claim 16, wherein said counterbearing is configured so as to be cruciform, comprising at least three arms that emanate from a center.
 18. The hob according to claim 17, wherein said arms are mutually equiangular.
 19. The hob according to claim 16, wherein said counterbearing comprises a shape of a curved disc and a central region, wherein said counterbearing in said central area is connected to said hot plate, and in an external region largely bears on said lower side of said hob plate.
 20. The hob according to claim 19, wherein said counterbearing comprises an opening for an electrical connector to said hot plate.
 21. The hob according to claim 16, wherein said hob comprises a hob plate from metal or stainless steel, respectively.
 22. A hob comprising: at least one hot plate comprising a hot-plate body, wherein: said hot-plate body comprises an upper side and a lower side; said hot-plate body is composed of metal; at least one heating element is disposed on said lower side of said hot-plate body; said upper side of said hot-plate body is configured so as to be flat, for setting up a cooking vessel to be heated; said hob comprises a hob plate comprising a hot-plate opening into which said hot plate is inserted; said hot plate by way of a laterally projecting periphery of said upper side of said hot-plate body projecting beyond said hot-plate opening; for fastening said hot plate to said hob, a counterbearing is attached to said hot plate from below and is centrically fastened or screwed to said hot plate; said counterbearing engages across said hot-plate opening and bears on said lower side of said hob plate at least three bearing points; and said bearing points being mutually spaced apart by an arc angle of at least 45°.
 23. The hob according to claim 22, wherein said counterbearing comprises a shape of a curved disc, and in a central region is connected to said hot plate, and in an external region largely bears on the lower side of the hob plate.
 24. The hob according to claim 23, wherein said counterbearing in said external region in a completely encircling manner bears on said lower side of said hob plate. 